"It was supposed to go down Northumberland Street but we ended up circling the Monument about six times.

"We're going to do more, this was just the first one. I think we created a good atmosphere among everyone."

The first Flash Mobs took place in New York City groups have since been set up all over the world.

Europe's first was in Rome when they gathered in a book shop and asked staff about books that did not exist.

The last New York flash mob caused havoc in the Toys R Us store where flash mobsters gathered for their sixth outing. They were told to stare at the store's giant dinosaur then fall to their knees and react to its roars.

What is a flash mob?

Flash mobs are a sudden gathering of people who do something unusual in unison then disperse.

They are organised for the fun of it and have a code of conduct, including no fancy dress.

The first took place last June at Macy's in New York when 100 people gathered around a rug in the 9th floor carpet department.